Novel chain-breaking antioxidants

ABSTRACT

Compounds, preferably 5-pyrimidinol and 3-pyridinol derivatives, that act as effective chain breaking antioxidants of both the lipid and water-soluble variety (analogous to the natural Vitamins E and C), many of which are more reactive toward peroxyl radicals than the most potent form of Vitamin E. These compounds may exhibit many chemopreventive effects associated with conditions in which free radical-mediated cellular damage or disruption is implicated and Vitamins E and C are shown to have protective effects. Additionally, these compounds should be excellent oxidation inhibitors as additives to fuels, lubricants, rubber, polymers, chemicals, solvents and foodstuffs.

This application claims benefit of co-pending U.S. Patent ApplicationSer. No. 60/213,826 filed Jun. 23, 2000, entitled “Derivatives of5-Pyrimidinols and 3-Pyridinols: Novel Chain-Breaking Antioxidants”.

FIELD OF THE INVENTION

The present invention relates to compounds, including derivatives of5-pyrimidinol and 3-pyridinol and any acid or base addition saltthereof, that are effective chain-breaking antioxidants both of thelipid and water-soluble variety and, in that regard, are analogous tothe natural Vitamins E and C. Hence, not only will the compounds of thepresent invention be excellent oxidation inhibitors as additives tofuels, lubricants, rubber, polymers, chemicals, solvents and foodstuffs,but they may also exhibit many chemopreventive effects associated withcancer, aging, heart and lung disease, inflammation, Alzheimer's andParkinson's disease, skin damage and any other conditions in which freeradical-mediated cellular damage or disruption is implicated and inwhich Vitamins E and C and other antioxidants are shown to haveprotective effects.

BACKGROUND OF THE INVENTION

Autoxidation of hydrocarbons and other organic materials is one of themost important chemical processes known. Since the 1960's, the mechanismof inhibition of this process by antioxidants has been extensivelystudied, and antioxidants are now a key additive to many hydrocarbonproducts, including fuels, lubricant oils, rubber, polymers, chemicals,solvents and foodstuffs. However, it has only been in the last twodecades that the importance of lipid peroxidation to human health hasbegun to become unearthed. Since then, substantial evidence hasaccumulated that implicate free radicals in aging, carcinogenesis andthe pathogenesis of many conditions including heart disease (e.g.atherosclerosis), lung disease (e.g. emphysema) and severalneurodegenerative disorders including Alzheimer's and Parkinson'sdiseases.

Consequently, the role of both enzyme and small-molecule antioxidantsand the mechanisms of their protective function have been extensivelystudied. For example, it is now well accepted that the key initial eventin the development of atherosclerosis involves free-radical mediatedoxidative modification of low-density lipoprotein (LDL).

In support of this, it has been shown that a high intake of Vitamin E(α-tocopherol, Formula 1 below), a potent lipid-soluble radical-trappingantioxidant, reduces the risk of coronary heart disease and that lowlevels of Vitamin E in serum correlate with an increased incidence ofmyocardial infarction. For example, see Gey, K. F. Nutr. Biochem., 1995,6, 206-236, incorporated herein by reference.

Furthermore, probucol (Formula 2, below), a radical-scavengingantioxidant, is widely used to treat hypercholesterolemia andatherosclerosis. For example, see Barkley et al. Drugs 1986, 37,761-800.

Given that antioxidants are of such tremendous industrial importance andhave also been shown to possess preventive properties on the incidenceof heart disease and many other degenerative diseases, various kinds ofnatural and synthetic antioxidants have been synthesized and studiedboth in vitro and in vivo. Unfortunately, few of them have demonstratedbetter radical-trapping activity than α-tocopherol, the majorlipid-soluble radical-trapping antioxidant in plasma and LDL.

Phenols (of which α-tocopherol is an example) are the most abundant andwidely used natural and synthetic antioxidants. Their mechanism ofaction as antioxidants, relies on their ability to transfer theirphenolic H-atom to a chain-carrying peroxyl radical (LOO., Reaction 1)at a rate much faster than that at which the chain-propagating step oflipid peroxidation proceeds (Reaction 2).

LOO.+ArOH→LOOH+ArO.   Reaction 1:

LOO.+LH→LOOH+L.(+O₂→LOO.)   Reaction 2:

A higher rate for Reaction 1 is expected with an increasingly weak ArO—Hbond, and thus as the exothermicity of Reaction 1 increases relative toReaction 2, one would expect that ArOH becomes a better chain-breakingantioxidant. Indeed, when the logarithm of the rate constant forReaction 1 (log k₁) is plotted against the phenolic O—H bonddissociation enthalpy (BDE) for several ArOH, a linear correlation ofBDE (kcal/mol)=97.44−2.93 log k₁(M⁻¹s⁻¹) is obtained. This correlationcan be used to predict the rate constants for the reaction of peroxylradicals with novel phenolic compounds whose O—H BDEs are known.

It is well-known that electron-donating (ED) groups substituted para andortho to the phenolic hydroxyl lower the O—H bond dissociation enthalphy(BDE) and increase the rate of H-atom transfer to peroxyl radicals.However, efforts to design new phenolic antioxidants with increasedrates of H-atom transfer to peroxyl radicals have remained unsuccessful.This is because, while the substitution of phenols with increasingly EDgroups (e.g., —NH₂ and —NH₂) decreases their O—H BDEs, it also decreasestheir ionization potentials (IPs) such that they react directly withoxygen.

In 1985, Ingold and Burton investigated aminophenols as potentialantioxidants. More specifically, they looked at Formula 3a and Formula3b, below, as potential chain-breaking antioxidants, but found Formula3a to be unstable in air and Formula 3b to react slowly with peroxylradicals compared to α-tocopherol. See Burton et al. J. Am. Chem. Soc.1985, 107, 7053-7065, incorporated herein by reference.

These results may be explained in that the steric interaction betweenthe meta-methyl and N-ethyl groups drives the N-ethyl group down out ofthe plane of the ring and removes the nitrogen lone pair fromconjugation with the aromatic ring. This abolishes its stabilizingeffect on the aryloxyl radical.

A known problem with aminophenols as antioxidants lies not only in thefact that they are very difficult to prepare and store, but also intheir toxicity. In the case of para-aminophenol, this is related to itsmetabolic activation (oxidation, by cytochrome P450 among otherpossibilities) to a reactive intermediate that reacts with nucleophilicresidues on proteins or DNA to form covalent intermediate that reactswith nucleophilic residues on proteins or DNA to form covalentintermediates or that can result in the depletion of glutathione stores.

Further substituted aminophenols (such as 4-N,N-dialkylaminophenol or4b, above) are toxic because their oxidation no longer requiresmetabolism, but only a direct reaction with molecular oxygen to yieldsuperoxide and the electrophilic species. This makes the compound apro-oxidant and possible mutagen/carcinogen/teratogen rather than anantioxidant.

Based upon the above observations, the present inventors decided that areasonable set of design criteria for new aminophenolic antioxidants arecompounds with: (1) low phenolic O—H BDEs such that they have large logk₁ value, but (2) high ionization potentials (IPs) such that they arenot reactive to molecular oxygen.

U.S. Pat. No. 4,554,276 to LaMattina discloses2-amino-5-hydroxy-4-methyl pyrimidines that are disclosed as beinguseful as inhibitors of leukotriene synthesis and for the treatment ofpulmonary, inflammatory and cardiovascular diseases, cancer andpsoriasis, and peptide ulcers.

U.S. Pat. No. 4,711,888 to Walker discloses hydroxy or alkoxypyrimidines that are disclosed as being inhibitors of leukotrienesynthesis and, as a result, are useful in the treatment of pulmonary,inflammatory, allergic, cardiovascular diseases, and peptide ulcers.

U.S. Pat. No. 5,187,175 to Belliotti et al., discloses 2-carbonylsubstituted-5-hydroxy-1,3-pyrimidines that are disclosed as being usefulas inhibitors of 5-lipoxygenase, and thereby providing a treatment forinflammation, arthritis, pain, fever, and the like.

U.S. Pat. No. 5,196,431 to Belliotti discloses 2-substitutedamino-4,6-di-tertiarybutyl-5-hydroxy-1,3-pyrimidines described as havingactivity as inhibitors of 5-lipoxygenase and/or cyclooxygenase providingtreatment for inflammation, arthritis, pain, and fever.

U.S. Pat. No. 5,220,025 to Belliotti et al. is a divisional of the '431patent discussed above.

U.S. Pat. No. 5,001,136 to Walker discloses 2-substitutedmethylamino-amino 5-(hydroxy or alkoxy) pyridines useful in thetreatment of pulmonary, inflammatory, dermatological, allergic andcardiovascular diseases.

U.S. Pat. No. 5,284,949 to Belliotti et al. discloses 2-substitutedamino-4,6-di-tertiarybutyl-5-hydroxy-1,3-pyrimidines described as havingactivity as inhibitors of 5-lipoxygenase and/or cyclooxygenase providingtreatment for inflammation, arthritis, pain, and fever.

U.S. Pat. No. 5,177,079, to Connor et al. describe2-substituted-4,6-di-tertiary-butyl-5-hydroxyl-1,3-pyrimidines disclosedas being useful as inhibitors of 5-lipoxygenase and/or cyclooxygenaseproviding treatment of conditions advantageously affected by suchinhibition including inflammation, arthritis, pain, fever.

SUMMARY OF THE INVENTION

The present invention relates to compounds, including derivatives of5-pyrimidinol and 3-pyridinol and any acid or base addition saltthereof, that are effective chain-breaking antioxidants both of thelipid and water-soluble variety, and in that regard, are analogous tonatural Vitamin E and C.

The present inventors have discovered that many 5-pyrimidinol and3-pyridinol derivatives act as effective chain-breaking antioxidants invitro. Their synthesis precludes that they may be prepared easily aseither of the lipid- or water-soluble variety (analogous to the naturalVitamins E and C). Furthermore, compounds of the present invention maybe significantly more reactive toward peroxyl radicals than the mostpotent form of Vitamin E (α-tocopherol). Furthermore, the compounds ofthe present invention are stable to air oxidation. In addition to theirindustrial applications, compounds of the present invention exhibit manychemopreventive effects associated with cancer, aging, heart and lungdisease, inflammation, Alzheimer's and Parkinson's disease and any otherconditions in which free radicals are implicated as being involved intheir pathogenesis.

Additionally, the compounds of the present invention are excellentoxidation inhibitors as additives to fuels, lubricants, rubber,polymers, chemicals, solvents and foodstuffs.

Accordingly, an object of the present invention is to provide a compoundof the following formula, and acid or base addition salts thereof:

wherein,

R₁ is selected from the group consisting of hydrogen, alkyl, amino,alkylamino, N,N-dialkylamino;

R₂ is selected from the group consisting of hydrogen, alkyl; and

R₃ is an electron-donating substituent.

Another object of the present invention is to provide a compound of thefollowing formula, and acid or base addition salts thereof:

wherein,

R₁ is selected from the group consisting of hydrogen, and, alkyl;

R₂ is selected from the group consisting of hydrogen, and alkyl;

R₃ is selected from the group consisting of hydrogen, and alkyl; and

R₄ is an electron-donating substituent.

Another object of the present invention is to provide a compound of thefollowing formula, and acid or base addition salts thereof:

wherein,

X is N—R₅ or 0;

R₁ is selected from the group consisting of hydrogen, and, alkyl;

R₂ is selected from the group consisting of hydrogen, alkyl;

R₃ is selected from the group consisting of hydrogen, alkyl;

R₄ is selected from the group consisting of hydrogen, alkyl;

R₅ is selected from the group consisting of hydrogen, alkyl; and

n is 1 or 2.

Another object of the present invention is to provide a method ofinhibiting the oxidation of compounds or mixtures comprising theaddition of an effective amount of at least one of the above compoundsto the compound or mixture.

Another object of the present invention is to provide a method ofreducing the oxidative environment in a petroleum composition selectedfrom the group consisting of lubricating compositions and liquid organicfuels, said method comprising adding to said petroleum composition aneffective amount of an antioxidant composition, said antioxidantcomposition comprising at least one of the above compounds.

Another object of the present invention is to provide a method ofinducing antioxidant activity in warm-blooded animals comprisingadministering to warm-blooded animals an antioxidatingly effectiveamount of a biologically active composition, the biologically activecomposition comprising at least one of the above compounds.

Finally, another object of the present invention is to provide a methodof treating free radical-mediated cellular damage in warm-bloodedanimals, comprising administering to warm-blooded animals anantioxidatively effective amount of at least one of the above compounds.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows correlations of σ_(p) ⁺ and the calculated gas phase O—Hbond dissociation enthalpies (298K) of 4-substituted phenols (•),6-substituted-3-pyridinols (∘), and 2-substituted-5-pyrimidinols (▾).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As stated above, an object of the present invention is to providecompounds that are chain-breaking antioxidants. Without being bound bytheory, incorporating nitrogen into the aromatic rings of phenoliccompounds, has the effort of stabilizing the parent phenol (by loweringthe highest occupied molecular orbital energy) while destabilizing theradical cation, thereby effectively raising the IP. The effect ofnitrogen in the aromatic ring would not greatly affect the O—H BDEbecause the effects on the parent and radical should be similar.Furthermore, a pyrimidine or pyridine ring may better stabilize apartial negative charge on the phenolic oxygen, which would result in afavorable polar effect in the transition states of hydrogen atomtransfer reactions. The greater charge separation would bring about afaster rate of reaction of alkyl, alkoxyl and peroxyl radicals withthese compounds over phenols with the same O—H BDE.

Using density functional theory model calculations recently developed byDiLabio and co-workers (see: DiLabio et al., J. Phys. Chem. A. 1999,103, 1653-1661 and DiLabio et al. J. Org. Chem. 2000, 65, 2195-2203) andexperimental measurements recently developed by Pedulli and co-workers(largely summarized in Lucarini et al., J. Am. Chem. Soc. 1999, 121,11546-11553) the reactivity of model 5-hydroxypyrimidine (5-pyrimidinol)and 3-hydroxypyridine (3-pyridinol) derivatives can be studied. Forexample, the present inventors have found that many of the compounds ofthe present invention have lower O—H BDEs than Vitamin E, but higher orsimilar IPs. This suggests that many of the compounds of the presentinvention should be at least as stable to air oxidation but yet morereactive to peroxyl and alkyl radicals than similarly substitutedphenols.

Furthermore, the reactivities of the compounds of the present inventionwith alkyl and peroxyl radicals indicate the presence of an anticipatedpolar effect in the transition state. Making the compounds of thepresent invention with the same O—H BDE's as phenolic compounds betterchain-breaking radical-trapping antioxidants.

Compounds of the present invention include compounds of formulae 4-6,below:

Preferred derivatives of Formula 4 can be divided into 2 groups. Theyinclude, but are not limited to those in group a:2-R₃-4-R₂-6-R₁-5-hydroxypyrimidines where R₁, R₂═H or alkyl; R₃=anyelectron-donating group, but most preferably alkoxy, amino, N-alkylaminoor N,N-dialkylamino; and those of group b:2-R₃-4-R₂-6-R₁-5-hydroxypyrimidines where R₁=amino, N-alkylamino, orN,N-dialkylamino; R₂═H or alkyl; R₃=any electron donating group, butmost preferably alkoxy, amino, N-alkylamino or N,N-dialkylamino. Thesepreferred derivatives are calculated to be at least 10 kcal/mol morestable than their 1,4-tautomers or 1,2-tautomers.

Preferred derivatives of Formula 5 include but are not limited to2-R₁-4-R₂-5-R₃-6-R4-3-hydroxypyridines where R₁, R₂, R₃═H or alkyl andR₄=any electron donating group, but most preferably alkoxy, amino,N-alkylamino or N,N-dialkylamino.

With regard to preferred alkyl groups adjacent to the active hydroxylgroup in Formula 4 and Formula 5, and not being bound by theory, it isbelieved that the tertiary-butyl groups result in a lower O—H BDE, buthinder the approach of peroxyl radicals or other substrates to thepyrimidinoxyl radical—this is important in preventingtocopherol-mediated peroxidation. The preferred methyl groups result ina slightly higher O—H BDE, but there is no steric hindrance to theapproach of peroxyl radicals or other substrates to the aryloxylradicals. The preferred alkyl groups on the exocyclic amine group arevaried from hydrogen to methyl to ethyl for greater electron-donationand hence weakening of the O—H bond. The tertiary-butyl group has thepotential to hinder any possible N-oxidation to the N-oxide bycytochrome P450 or N-methylation by N-methyl transferases althoughlittle precedent for this exists in the literature. Pentyl, octyl andphytyl groups make the compound increasingly lipid-soluble. Di-pentyland di-octyl compounds allow for greater mobility within and betweenmembranes compared to Vitamin E. The di-phytyl moiety firmlyincorporates and retains the molecule in the membrane or lipoproteinparticle.

Preferred derivatives of Formula 6 are for n=2, X=N—R₅(6-hydroxy-2-R₃-2-R₄-5-R₂-7-R₁-1-R₅-2,3,4-trihydro-[1,8]-naphthiridine)and n=1, X═N—R₅(5b-hydroxy-2-R₃-2-R₄-4b-R₂-6b-R₁-1-R₅-pyrrolo-[2,3-b]-pyridine) arequinoline and indole derivatives of pyridines where R₁, R₂, R₃, R₄, R₅═Hor alkyl. Derivatives where n=2 or 1 and X═O and R₁, R₂, R₃, R₄═H oralkyl may also be particularly useful.

Preferably, with respect to Formulas 4-6, above, preferred substituentsare electron-donating groups that may donate via direct conjugation orhyperconjugation, electron density to the aromatic ring, therebydestabilizing the molecular orbitals of π-symmetry in the parent, andstabilizing them in the radical. For example, any substituent groupwhose Hammett substituent constant, sigme-plus, is less than zero. SeeHansch et al., Chem. Rev., 1991, 91, 165-195. Electron-donatingsubstituent groups include but are not limited to alkyl, phenyl, alkoxy,acyloxy, hydroxy, amino, alkylamino, dialkylamino.

Preferred compounds of Formula 4, above, include compounds of Formula 7,below. Preferred compounds of Formula 5, above, include compounds ofFormula 8 and 9, below.

Preferred derivatives of formula 7 and 8 are2-N,N—R₁,R₂-amino-4-R₃-6-R₃-5-hydroxypyrimidines (R₁, R₂═H,methyl,ethyl, t-butyl, pentyl, octyl, phytyl; R₃═H, methyl, t-butyl) and4-N,N—R₁,R₂-amino-2-R₃-3-hydroxypyridines (R₁═H, methyl, ethyl, t-butyl,pentyl, octyl, phytyl; R₂═H, methyl, ethyl, t-butyl, pentyl, octyl,phytyl; R₃═H, methyl, t-butyl), respectively.

With regard to the preferred alkyl groups ortho to the hydroxyl group,and not being bound by theory, it is believed that the t-butyl groupsresult in a lower O—H BDE, but hinder the approach of peroxyl radicalsor other substrates to the pyrimidinoxyl radical—this is important inpreventing tocopherol-mediated peroxidation. The preferred methyl groupsresult in a slightly higher O—H BDE, but there is no steric hindrance tothe approach of peroxyl radicals or other substrates to thepyrimidinoxyl radicals. The preferred alkyl groups on the exocyclicamine group are varied from hydrogen to methyl to ethyl for greaterelectron-donation and hence weakening of the O—H bond. The preferredt-butyl group has the potential to eliminate any possible N-oxidation tothe N-oxide by cytochrome P450 or N-methylation by N-methyl transferasesalthough little precedent for this exists in the literature. Thepreferred pentyl, octyl and phytyl groups make the compound increasinglylipid-soluble. The di-pentyl and di-octyl compounds allow for greatermobility within and between membranes compared to Vitamin E. Thedi-phytyl moiety firmly incorporates and retains the molecule in themembrane or lipoprotein particle.

Preferred derivatives of Formula 9(2-N,N—R₁,R₂-amino-6-R₃-4-N,N—R₄,R₅-amino-5-hydroxypyrimidine) are R₁═H,methyl, ethyl, t-butyl, pentyl, octyl, phytyl; R₂═H, methyl, ethyl,t-butyl, pentyl, octyl, phytyl; R₃, R₄, R₅═H, methyl, t-butyl). It isbelieved that these preferred derivatives compounds are 10 kcal/mol morestable than their 1,4-tautomers, and that the 3-hydroxypyridines (6,8,9)are 8-10 kcal/mol more stable than their amide tautomers.

Preferred embodiments of Formula 6, above, include compounds of Formulae10 and 11, below.

Preferred derivatives of compounds 10(6-hydroxy-2-R₂-2-R₄-5-R₃-7-R₃-1-R₁-2,3,4-trihydro-[1,8]-naphthiridine)and 11 (5b-hydroxy-2-R₂-2-R₄-4b-R₃-6b-R₃-1-R₁-pyrrolo-[2,3,b]-pyridine)are quinoline and indole derivatives of pyridines (R₁═H, methyl; R₂═H,methyl, ethyl, t-butyl, pentyl, octyl, phytyl; R₄═H, methyl, ethyl,t-butyl, pentyl, octyl, phytyl; R₃═H, methyl, t-butyl, hydroxy). R₃ mayalso be hydrogen because it may be important for at least one positionto be kept vacant so that hemolytic aromatic substitution, for exampleby nitrogen dioxide, can occur, and the adduct could be subsequentlyeliminated.

The synthesis of 5-pyrimidinols has been described both in thescientific and patent literature. Simple compounds such as 5-pyrimidinolitself can be obtained readily via displacement of the appropriatelysubstituted 5-bromopyridine with methoxide in methanol, followed bydeprotection to yield the 5-pyrimidinol (see EXAMPLE 1, below, andBredreck et al. Chem. Ber. 1958, 91, 2832). Alternatively, the bromidecan be converted to the hydroxyl directly upon treatment with bariumhydroxide and a copper catalyst (see Bray et al. Biochem. J. 1951, 48,400). A variety of 2,4,6-alkyl-substituted-5-pyrimidinols can beprepared from substituted 5-carbonyloxazoles (see EXAMPLES 2 and 3,below, and Dornow and Hell Chem Ber. 1960, 1998) or from theappropriately substituted 5-bromopyrimidines as described above.Additionally, a variety of 4-alkoxy-substituted-5-pyrimidinols can beprepared from condensation of 3-acyloxy-2,4-pentanediketones withO-alkylisoureas, as shown in EXAMPLE 4, below.

Furthermore, from appropriately-substituted pentanediketones, a varietyof amino and dialkyl amino substituted-5-pyrimidinols can be obtainedupon condensation with 1,1-dialkylguanidines similar to in EXAMPLE 4(see EXAMPLE 5) or again, the bromide can be converted to the hydroxylas described above. Ortho-amine substituted-5-pyrimidinols (9) can beprepared from the appropriately substituted precursor with a vacantortho position and subjected to Chichibabin conditions, i.e., aminationby alkali-metal amides (for a review, see: Vorbruggen Adv. Heterocycl.Chem. 1990, 49, 117-192).

The synthesis of 3-pyridinols have also been well documented in theliterature. Simple 3-pyridinols can either be purchased from commercialsources or prepared from the precursor 3-bromopyridine analogous to thesynthesis of 5-pyrimidinols from 5-bromopyrimidines. The more complexsubstitution patterns may be achieved by someone skilled in the art, ina variety of ways described in the scientific literature (see, forexample: Pyridine and its Derivatives, Part 3, Erwin Klingsberg, Ed.Interscience Publishers, 1962). For example,6-amino-2,4-dimethyl-3-hydroxypyridine may be prepared from the DielsAlder reaction of methacrylonitrile and 2-amino-5-methyloxazole (see:Hayakawa et al. Chem. Pharm. Bull. 1984, 32, 4914). Alternatively,treatment of the 6-amino-2,4-dimethyl-3-bromopyridine with bariumhydroxide in the presence of a copper catalyst yields the product [see:Bray et al., Biochem. J. 1951, 400). Compounds such as 6, 10 and 11 canbe prepared from the lithiation of the 2-amino pyridine, followed bytreatment with a terminal dibromoalkane.

The following examples are given for illustrative purposes and are notintended to be limiting the present invention.

Example 1 5-Pyrimdinol

Preparation of 5-methoxypyrimidine. A Parr bomb is charged with 15 g(0.094 mol) of 5-bromopyrimidine and 5.4 g (0.10 mol) of sodiummethoxide in 170 ml of methanol. The whole is heated at 100-120° C. for16 hours. The deep brown mixture is neutralized with glacial acetic acidand extracted three times with ether. The combined organic layers arethen dried over Na₂SO₄ and concentrated in vacuo. The resulting brownsolid is purified by column chromatography on silica gel using 9:1 ethylacetate:hexane as eluent. The pyrimidine is thus obtained as pale yellowcrystals (7 g, 70%). Alternatively, purification can be accomplished bydistillation bp (10 mm/Hg) 76°.

Preparation of 5-pyrimidinol. In a three-necked flask cooled with ice ispoured 3.38 g sodium hydride (3.38 g, 140.9 mmol) as a 60% suspension inmineral oil and dry DMF (60 ml). Ethanethiol (4.38 g, 70.48 mmol) isadded dropwise and evolution of hydrogen is observed. After 15 minutes,5-methoxypyrimidine (3.8 g, 35.3 mmol) is added and the resultingmixture is heated at 100° C. for 4 hours. A generous stream of argon isbubbled through during the reaction, and the head of the refluxcondenser is connected with a cold trap charged with mCPBA indichloromethane (in order to trap and oxidize the sulfide produced). Thedeep brown suspension is cooled with ice and the reaction is quenchedwith water (100 ml) neutralized with acetic acid and partitioned withethyl acetate (4×100 ml). The organic layers are dried in vacuo and theresidual yellow solid is purified by column chromatography using ethylacetate as eluent. The compound is thus obtained as white needles. Ayellow color is due to the presence of methyl-ethylsulfide and could becrystallized from dioxane to yield 1.7 g in 50% yield.

Example 2 2,4,6-Trimethyl-5-pyrimidinol

Preparation of 2,4-dimethyl-5-acetyloxazole. Chloroacetylacetone 8 g(59.4 mmol) is dissolved in 70 ml of glacial acetic acid and ammoniumacetate 13.7 g (178.2 mmol) is then added and the mixture is refluxedfor 4 hours. The solution is cooled, brought to pH 5 and extracted intoether; the organic layer is dried over Na₂SO₄ and concentrated todryness in vacuo. The residue is purified by column chromatography onsilica gel using 8:2 hexane:ethyl acetate as eluent. The2,4-dimethyl-5-acetyloxazole is obtained as orange needles (2.2 g, 27%).

Preparation of 2,4,6-trimethyl-5-pyrimidinol. The2,4-dimethyl-5-acetyloxazole is poured into a Parr Bomb with 20 ml (51mmol) of concentrated ammonium hydroxide and brought to 180° C. in threehours. Heating is continued for 10 hours, and after cooling the mixtureis brought to pH 5 with HCl, extracted into ether, dried over Na₂SO₄ andstripped in vacuo. The residual solid is crystallized from benzene togive pale yellow crystals (1.3 g, 60%).

Example 3 2-Methyl-4,6-di-tert-butyl-5-pyrimidinol

Preparation of 2-methyl-4-tert-butyl-5-tert-butyl carbonyl oxazole.4-Bromo-2,2,6,6-tetramethylheptane-3,5-dione (1.5 g, 5.7 mmol) preparedaccording to the method reported by Shoppe and Stevensons, J. Chem. Soc.Perk. Trans. I 3015 (1972) is dissolved in glacial acetic acid (60 ml);ammonium acetate (2.6 g 34.2 mmol) is added and the mixture is refluxed27 hours. The clear orange solution is diluted with water (60 ml),brought to pH 5 with NaOH 0.5 M and extracted with ethyl acetate (3×25ml). The organic phase is dried with sodium sulfate and evaporated invacuo. The oxazole is thus obtained as a deep orange oil, later purifiedon a pad of silica gel eluted with hexane/ethyl acetate 8:2. The yieldwas 1.25 g (98%).

Preparation of 2-methyl-4,6-di-tert-butyl-5-pyrimidinol. The2-methyl-4-tert-butyl-5-tert-butyl carbonyl oxazole (1.25 g, 5.6 mmol)is poured into a Parr Bomb with concentrated ammonium hydroxide (100 ml)and heated at 180° C. for 36 hours. The excess ammonia is evaporated andthe pH of the solution is adjusted to 6 with 37% HCl; the resultingsolution is extracted into ether (3×25 ml) and the organic layer isdried with sodium sulfate and evaporated in vacuo. Chromatography onsilica gel eluting with 8:2 hexane:ethyl acetate afforded the desiredpyrimidine as white crystals (0.87 g, 70%).

Example 4 2-Methoxy-4,6-dimethyl-5-pyrimidinol

Preparation of benzoic acid 1-acetyl-2-oxo-propyl ester. Sodium benzoate(106.5 g, 0.74 mol) is suspended in 500 ml of dry DMSO in a three neckedflask equipped with a mechanical stirrer and under a gentle stream ofargon. Chloroacetylacetone (50 g, 0.37 mol) is then added and theresulting orange mixture is stirred vigorously. After 3 hours thereaction is complete (TLC hexane/ethyl acetate 8/2); the melange iscooled by means of iced water and diluted with 500 ml of water. Thesolution is then extracted into ether (3×400 ml), washed with water (2×1L), dried over Na₂SO₄ and concentrated to dryness in vacuo. Theresulting viscous orange oil is pure enough for the next step. The yieldis 81.4 g (100%).

Preparation of 2-methoxy-4,6-dimethyl-5-benzyloxy pyrimidine. Thebenzoic acid 1-acetyl-2-oxo-propyl ester 3.2 g (14.9 mmol) is dissolvedin 50 ml of dry DMF in a three-necked flask under argon. Sodium acetate2.4 g (29.8 mmol) and O-methyl isoureahydrogensulfate 2.56 g (14.9 mmol)are then added and the mixture is heated at 65° C. for 24 hours. Thereaction mixture is cooled with ice and quenched with water, and thenneutralized with glacial acetic acid and extracted into ether. Theorganic layer is dried over Na₂SO₄ and concentrated to dryness in vacuo.The residual solid is purified by column chromatography on silica gelusing 8:2 hexane:ethyl acetate as eluent. The yield is 0.7 g (20%).

Preparation of 2-methoxy-4,6-dimethyl-5-pyrimidinol. The2-methoxy-4,6-dimethyl-5-benzyloxy pyrimidine 0.7 g (2.7 mmol) isdissolved in 10 ml of ethanol with 0.3 g (5.4 mmol) of KOH. The whole isrefluxed for 11 hours, and after cooling the reaction is diluted with 20ml of water and brought to pH 5 with glacial acetic acid. The mixture isextracted into ethyl acetate (3×25 ml), dried over Na₂SO₄ and strippedin vacuo. The resulting solid is purified by column chromatography onsilica gel using 9:1 hexane:ethyl acetate as eluent. The yield is 0.4 g(98%).

Example 5 2-N,N-Dimethylamino-4,6-dimethyl-5-pyrimidinol

Preparation of 3-acetoxy-2,4-pentan-2,4-dione. 3-chloro-2,4-pentanedione(10 g 74.6 mmol) is dissolved in dry DMSO; sodium acetate (12.2 g 149.2mmol) is added and the mixture is kept at room temperature. After a fewminutes the solution turns a deep orange-red color, and after two hoursis complete. Water is added, the solution is partitioned with ether(3×50 ml) and the combined organic layers are dried with sodium sulfateand evaporated in vacuo. The resulting orange oil is purified on a padof silica gel eluting with 8:2 hexane:ethyl acetate. The yield is 9.2 g(80%).

Preparation of N,N-dimethylamino-4,6-dimethyl-5-pyrimidinol. The titledacetoxyketone (1 g, 6.3 mmol) is dissolved in dry DMF under a nitrogenatmosphere; sodium acetate (1 g 12.6 mmol) and 1,1-dimethylguanidinesulfate (1.7 g, 6.3 mmol) are added and the mixture is kept at 100° C.for 4 h. The resulting orange suspension is diluted with water andextracted with ethyl acetate (3×25 ml), the organic layer is dried withsodium sulfate and evaporated in vacuo. Purification by chromatography(8:2 hexane:ethyl acetate) gave a yellow oil which crystallized oncooling; yield 50%. Deacetoxylation with alcohlic NaOH afforded thepyrimidinol in 50% of yield (yellow needles from benzene/light petroleumbenzene).

TABLE A Properties of Examples Important for Antioxidant Efficacy.Example O—H BDE k/alkyl k/peroxyl 1 91.3 ^(a) 3.6 × 10⁶ ^(b) 2 85.2 4.6× 10⁵ 3.3 ± 0.4 × 10⁴ 3 84.1 3.2 ± 0.5 × 10⁴ 2.2 ± 0.3 × 10⁴ 4 82.5 ^(c)^(c) 5 78.2 2.9 ± 1.1 × 10⁶ 8.6 ± 0.5 × 10⁶ O—H BDE: O—H bonddissociation enthalpy; k/alkyl: second order rate constant for reactionwith alkyl radicals; k/peroxyl: second order rate constant for reactionwith peroxyl radicals. ^(a) Estimate based upon other results to datefor other 5-pyrimidinols. ^(b) No induction period. ^(c) Not performed.

As stated above, it is well-known that electron-donating (ED) groupssubstituted para and ortho to the phenolic hydroxyl lower the O—H bonddissociation enthalphy (BDE) and increase the rate of H-atom transfer toperoxyl radicals. However, efforts to design new phenolic antioxidantswith increased rates of H-atom transfer to peroxyl radicals haveremained unsuccessful. See, for example, Burton et al., J. Am. Chem.Soc., 1985, 107, 7053-7065; and Wright et al., Cancer Detect. Prev.,1988, 22, 204.

For example, an aza-analogue of ∝-TOH (compound (ii), below) and9-hydroxy-julodine (compound (iii), below) were both unsatisfactory whenused as antioxidants because they reacted directly with oxygen viaelectron transfer. In an effort to increase the stability of highlyreactive, electron-rich phenols under conditions where oxygen ispresent, the present inventors incorporated nitrogen into the phenolicring.

Compounds:

The present inventors have developed a density functional theory (DFT)model ((RO)B3LYP/6-311+G(2d,2p)//AM1/AM1) which predicts X—H bondenergetics (X═C,N,O, and S) for several types of compounds, includingphenols, generally to within experimental error. See DiLabio et al., J.Phys. Chem. A., 1999, 103, 1653-1661. A second model,(B3LYP/6-31G(d)//AM1/AM1), evaluates the IPs of polysubstitutedaromatics. See DiLabio et al., J. Org. Chem., 2000, 65, 2195-2203. Usingthese two DFT models, the substituent effects on the O—H BDEs and IPs of3-pyridinol (v) and 5-pyrimidinol (vi) can be calculated relative tothose we have for phenol (iv).

While substitution of N for C at the 3-position of (iv) to give (v)increases the calculated IP from 195.4 to 206.4 kcal/mol (87.1 to 88.2kcal/mol). Introducing a second N at the 5-position to give (iv) furtherraises the IP and O—H BDE to 219.7 and 89.6 kcal/mol, respectively.Thus, despite the increase in IP of 24.3 kcal/mol from (iv) to (vi), theO—H BDE increases by only 2.5 kcal/mol. When the effects ofpara-substituents on the IPs and O—H BDEs in phenols,6-substituted-3-pyridinols, and 2-substituted -5-pyrimidinols arecalculated, it is found that the substituent effects on their O—H BDEs(FIG. 1) and IPs (not shown) are conserved.

Finally, the O—H BDEs and IPs of further-substituted 5-pyrimidinols werecalculated (the 3-pyridinols will be considered separately in aforthcoming publication). The results are presented in Table 1, below,along with those of their phenolic analogues and α-TOH for comparison.

TABLE 1 Calculated Substituent Effects on Gas Phase O—H BDEs at 298 Kand Adiabatic IPs at 0 K of Symmetrically Substitued Phenols (4) and5-Pyrimidinols (6)^(@) 2 x ortho para 6 4 H H (89.6)/(219.7) (87.1)/(195.4) H CH₃ −2.8/−10/4 −2.5/−8.5 CH₃ CH₃ −6.4/−22.7 −6.7/−17.1 H OCH₃ −6.0/−21.6  −6.1/−18.9 CH₃ OCH₃ −9.8/−31.4−10.1/−26.2 H N(CH₃)₂ 11.3/−45.1 −10.1/−37.7 CH₃ N(CH₃)₂ −15.5/−52.7 −14.8/−43.1 a-TOH (1) a Data presented BDE/IP in kcal/mol. Absolutevalues for unsubstituted 6 and 4 are in parentheses.a Data presented BDE/IP in kcal/mol. Absolute values for unsubstituted 6and 4 are in parentheses.

Increasing both the number and strength of ED substituents in the orthoand para positions brings about a steady decrease in the O—H BDE and IP.Consistent with the data in FIG. 1, the substituent effects on both theO—H BDE and IP are roughly the same for both compounds.

Our calculations suggest that 5-pyrimidinols should be effective H-atomdonors with the advantage of being much more stable to air oxidationthan similarly substituted phenols. To confirm this, we prepared four5-pyrimidinols (vi(a)-vi(d) as per procedures set forth by Bredereck etal., Chem. Ber., 1958, 91, 2832; Dornow et al., Chem. Ber., 1960, 93,1998; Conner et al., U.S. Pat. No. 5,117,079; and Walker et al., U.S.Pat. No. 4,711,888; respectively. The O—H BDEs were measured by EPRequilibration studies in the presence of a reference substituted phenol.Absolute measured values (±2 SD) were: 85.2±0.5 kcal/mol for (vi-b),84.10±0.25 kcal/mol for (vi-c), and 78.16±0.25 kcal/mol for (vi-d). Asshown in Table 2, these results preliminarily indicate that substituenteffects on the O—H BDE are roughly the same on going from phenols to5-pyrimidinols.

TABLE 2 Experimental Substituent Effects on Solution-Phase O—H BDEs at298 K of Substituted 5-Pyrimidinols (vi) and Phenols (iv) ^(a) 2 x orthopara (vi) (iv) ^(c) a H H (91.1) (88.3) b CH₃ CH₃ −5.9 −5.6 c t-Bu CH₃−7.0 −7.3 d CH₃ N(CH₃)₂ −12.9 ^(d) a-TOH (1) −10.0 ^(c) ^(a) All valuesin kcal/mol. Absolute values for Unsubstituted (vi) and (iv) are inparentheses. ^(b) Estimate (see text). Could not be measured due to theshort lifetime of the 5-pyrimidinoxyl radical. ^(c) From ref 2C. ^(d)Not an air-stable compound.

Regarding the O—H BDE of the unsubstituted 5-pyrimidinol, estimatedresults for (vi-b) and (vi-c) when compared to their phenolic analoguesof 91.1 kcal/mol for the O—H BDE in (vi-a) are in good agreement withour calculated value of 89.6 kcal/mol. We expect this estimate to bereliable to ±1 kcal/mol.

The data indicates that (vi-d) has a lower O—H BDE than a-TOH by boththeory (−0.7 kcal/mol) and experiment (−0.1 kcal/mol), but a much highercalculated IP (by 7.7 kcal/mol). This suggests that (vi-d) will transferits phenolic H-atom to free radicals at least as fast as a-TOH, but bemuch more stable to air oxidation. Additionally, (vi-d) is easilyprepared, handed, and purified in an open atmosphere without degradationby air oxidation—a problem commonly encountered when handling α-TOH.

Rate constants for the reactions of (vi-b-c) with alkyl radicals aredetermined by competition kinetics in benzene with one of either the5-hexenyl cyclization (see Chatgilialoglu et al., J. Am. Chem. Soc.,1981, 103, 7739), k_(r)=1.5×10⁵ s⁻¹ or neophyl radical rearrangement(see Franz et al., J. Am. Chem. Soc., 1984, 106, 3964-3967; and Burtonet al., J. Org. Chem., 1996, 61, 3778-3782), k_(r)=1.1×10³ as radicalclock (Table 3). Despite higher O—H BDEs for (vi-b) and (vi-c) withrespect to their phenolic counterparts, their rates of reaction withalkyl radicals were substantially faster.

TABLE 3 Reactivities of Substituted Phenols and 5-Pyrimidinols to Alkyl(298 K) and Peroxyl Radicals (323 K) in Benzene^(a) alkyl peroxyl 6b 4.6× 10⁵ (N)^(c,d) 3.3 ± 0.4 × 10⁴ 4b 8.5 ± 0.2 × 10⁴ (N)^(e) 1.1 ± 0.1 ×10⁵ 6c 3.2 ± 0.5 × 10⁴ (N) 2.2 ± 0.3 × 10⁴ 4c 4.8 ± 1.5 × 10³ (N)^(e)1.8 ± 0.3 × 10⁴ 6d 2.9 ± 1.1 × 10⁶ (H) 8.6 ± 0.5 × 10^(6f) a-TOH (1) 6.0± 1.5 × 10⁵ (H)^(e) 4.1 ± 0.4 × 10⁶ ^(a)Radical clocks used for thereactions with alkyl radicals are indicated in parentheses. ^(b)All rateconstants are second order with units of M⁻¹ s⁻¹. Errors represent ±2SD. ^(b)H = 5-hexenyl, N-neophyl. ^(c)Estimate based on correlations ofk and β for CH₃CN (k = 5.8 × 10⁴), EtOAc (K = 8.6 × 10³) and t-BuOH (K =4.9 × 10³).⁹ ^(d)In 1-5% D₂O, CH₃CN, k- 1.95 ± 0.7 × 10⁴.^(d)Measurements made by L. V. and reported in ref 12. ^(f)InD₂O-saturated benzene, k = 2.8 ± 0.6 × 10⁶.

Also, (vi-d), which has only a marginally lower O—H BDE than α-TOH,reacted 5 times faster with alkyl radicals. An explanation of theseresults may be given in terms of a polar effect in the transition stateof the atom-transfer reaction. See Walling, Free Radicals in Solution,Wiley: New York, 1957. The pyrimidine ring better supports a partialnegative charge on the aryloxyl oxygen than a phenyl ring, providingbetter charge separation in the transition state for H-atom transfer,and lowering the barrier to reaction for pyrimidinols compared tophenols with the same O—H BDE.

The reactivities of (vi-b) and (vi-c) with peroxyl radicals weremeasured by oxygen consumption experiments (see Lucarini et al., J. Org.Chem., 1998, 63, 4497-4499), studying the inhibited autoxidation ofstyrene in benzene, and the results were compared to the values measuredfor 4b-c and α-TOH under the same experimental conditions. Since therate constants for reactions with peroxyl radicals are within a factorof 3 for (vi-b)/(iv-b) and roughly the same for (vi-c)/(iv-c), a polareffect might still be involved to balance the BDE difference of 2.5-3kcal/mol. It is, however, a smaller effect as the peroxyl oxygen cannotsupport a partial positive charge in the transition state as effectivelyas the alkyl carbon.

The reactions of (vi-b) with alkyl radicals and (vi-d) with peroxylradicals were also performed in dry solvents containing D₂O to obtainthe deuterium kinetic isotope effect (k_(H)/k_(D)) for these reactions.In both cases, k_(H)/k_(D)=3.1, consistent with a primary isotope effectand suggesting that H-atom transfer is indeed the mechanism of reactionbetween alkyl or peroxyl radicals and the pyrimidinols.

In conclusion, by incorporating nitrogen into the aromatic ring, it ispossible to substantially increase the IPs of phenolic compounds withoutgreatly affecting their O—H BDEs. The substituent effects upon the O—HBDEs and IPs in these compounds are roughly the same as in phenol,making it possible to design novel compounds that undergo fastH-atom-transfer reactions with radicals, but which are stable to airoxidation. Moreover, the apparent presence of a kinetic polar effect inthe H-atom-transfer reactions to chain-carrying radicals makes5-pyrimidinols more effective chain-breaking antioxidants than phenolshaving the same O—H BDE.

The compounds of the present invention may be made combined withcarriers to form compositions appropriate for the particular end use.That is, the compounds of the present invention may be administered to asubject in need of treatment by a variety of conventional routes ofadministration, including oral, by injection, and topical. Preferably,oral administration is by using a gel capsule.

For example, the compounds of the present invention may be made intopharmaceutical composition with an appropriate carrier easily determinedby one of ordinary skill in the art and formed into a gel capsule bystandard methods known in the art.

All the formulations with compounds of the present invention may beconveniently presented by any of the methods well-known in the art ofpharmacy. Additionally, it will be readily apparent that the amountrequired of the compounds of the present invention will vary dependingon the particular compound, the route of administration, and theparticular treatment desired.

For topical use, the compounds of the present invention may beformulated in solutions, suspensions, gels, creams, or ointments.

As stated above, an embodiment of the present invention is to provide amethod of inducing antioxidant activity in warm-blooded animalscomprising administering to warm-blooded animals an antioxidatinglyeffective amount of a biologically active composition comprising acompound selected from the group consisting of formulae 4-11.

Another embodiment of the present invention is to provide a method oftreating a pathological condition involving an oxidative stressassociated with an overproduction of oxidizing free radicals, comprisingadministering an antioxidatively effective amount of an antioxidantcomprising a compound selected from the compounds of formulae 4-11.

Another embodiment of the present invention is to provide a method ofpreventing free radical-mediated cellular damage in warm-bloodedanimals, comprising administering to warm-blooded animals anantioxidatively effective amount of a compound of formulae 4-11.

The above methods include methods of therapy involving protection oforgans from oxidative damage induced by lipid peroxidation comprisingadministering to a subject in need of such therapy an effective amountof a compound of the formulae 4-11, or a pharmaceutically acceptablesalt thereof. The organ to be protected includes the cardiovascularsystem or cerebral tissue. Furthermore, the subject to be treated may berecovering from myocardial infarction, or may be suffering from lungdisease such as, for example, emphysema.

Additionally, the subject may have been deemed to have a predispositionfor or is displaying or experiencing symptoms consistent withParkinson's, Alzheimer's or other neurodegenerative disorder.

Another embodiment of a therapy for the above-described methods includesa therapy for treating a condition involving inhibiting the productionof reactive oxygen species by activated neutrophils comprisingadministering to a subject in need of such therapy an effective amountof the compounds of the formulae 4-11, or a pharmaceutically acceptablesalt thereof. This condition may be selected from the group consistingof psoriasis, inflammatory diseases or disorders, and AIDS.

Yet another embodiment of the above-described methods includesadministering to a patient having need thereof, a compound of formulae4-11 for the treatment of atherosclerosis and chronic inflammatorydisorders; for inhibiting the peroxidation of LDL lipid; for loweringplasma cholesterol, and treating cardiovascular disease.

By way of example, the cardiovascular diseases include, but arecertainly not limited to, thromboembolic disease, artherosclerosis, lowdensity lipid oxidation, adhesion of monocytes to endothelial cells,foam-cell formation, fatty streak development, platelet adherence,platelet aggregation, smooth muscle cell proliferation, and reperfusioninjury.

Also by way of example, the inflammatory diseases asthma, chronicinflammation, rheumatoid arthritis, autoimmune diabetes, transplantrejection, and tumor angiogenesis.

Another embodiment of the present invention related to a method ofinhibiting oxidation of fuels, petroleum products, lubricants, rubber,polymers, chemicals, solvents, and foodstuffs. Therefore, the presentinvention includes a method of inhibiting the oxidation of compounds ormixtures comprising the addition of an effective amount of a compound offormulae 4-11 to said compound or mixture. The compound or mixture maybe any base oil or mixture thereof suitable for the intended use of alubricant. Also, the base oil may is selected from the group consistingof a conventionally refined mineral oil, an oil derived from coal tar orshale, a vegetable oil, an animal oil, a hydrocracked oil, or asynthetic oil, or any mixture thereof. By way of example, synthetic oilsinclude include hydroisomerised paraffins, polyalphaolefms, polybutene,alkylbenzenes, polyglycols, esters such as polyol esters or dibasiccarboxylic acid esters, alkylene oxide polymers, and silicone oils. Anypetroleum product that autoxidizes is included.

In one embodiment, the compounds of the present invention may be used inthe manner disclosed in U.S. Pat. No. 6,096,695 to Lam et al. withrespect to being part of a effective antioxidant in lubricating oils.That is, the compounds of the present invention may be combined with theoil products in the manner suggested in the '695 patent, incorporatedherein by reference.

Additionally, the compounds of the present invention may be combinedwith lubricating oil in the manner suggested in U.S. Pat. No. 4,946,610,incorporated herein by reference.

In that regard, the method of the present invention includes a method ofreducing the oxidative environment in a petroleum composition selectedfrom the group consisting of lubricating compositions and liquid organicfuels, said method comprising adding to said petroleum composition aneffective amount of an antioxidant composition, said antioxidantcomposition comprising a compound formulae 4-11.

Also see U.S. Pat. No. 6,114,572 to Parker et al., incorporated byreference. The compounds of formulae 4-11 can be used, in a mannersimilar to the Parker compounds, as chemical antioxidant additives inorganic materials normally subject to oxidative deterioration, such as,for example, rubber, plastics, fats, petroleum products and the like. Ingeneral, a preservative amount of a compound of formulae 4-11, which issufficient in concentration to inhibit oxidative deterioration of thematerial to be protected, is admixed with the material subject tooxidation. The preservative amount of a compound of formula (1) willgenerally vary from about 0.01% to about 1.0% by weight.

Thus, another method of the present invention is inhibiting theoxidation of natural or commercial materials and products or chemicalconstituents thereof where compounds of the formulae 4-11 may be added,blended, sprayed, adhered, used to cover or impregnation of suchproducts as foods (e.g. modified milk, chewing gum), feed (e.g. forlivestock and other farm animals), agricultural products, drugs (e.g.oxidation inhibiting agent), non-medical drugs (e.g. preventive agent),cosmetics (e.g. hair liquid, cream, emulsion) and the raw materialsthereof.

As stated in the '512 patent, the method of the present inventionincludes inhibiting the polymerization of compounds comprising theaddition of an effective amount of compounds of the formulae 4-11 to thecompound or mixture of compounds. By way of example, the product may beany of the wide variety of monomer types which undergoes free radicalpolymerization. Examples of said monomers include those leading topolyethylene, poly(vinyl chloride), polystyrene, styrene-butadienerubber, butadiene-acrylonitrile copolymer,acrylonitrile-butadiene-styrene copolymer, polychloroprene, poly(methylmethacrylate), polyacrylonitrile, poly(vinyl acetate), poly(vinylidenechloride), poly(acrylic acid), poly(methacrylic acid), polyacrlyamide,polytetrafluoroethylene, polytrichlorofluoroethylene, poly(vinylidenefluoride), poly(vinyl fluoride) and allyl resins.

This invention thus being described, it will be obvious that the samemay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the present invention, and allsuch modifications as would be obvious to one of ordinary skill in theart are intended to be included within the scope of the followingclaims.

All cited patents and publications referred to in this application areherein expressly incorporated by reference.

1. A compound of the following formula, and acid or base addition saltsthereof:

wherein, R₁ is selected from the group consisting of hydrogen, alkyl,amino, alkylamino, and N,N-dialkylamino; R₂ is selected from the groupconsisting of hydrogen and alkyl; and R₃ is an electron-donatingsubstituent.
 2. A method of inducing antioxidant activity inwarm-blooded animals comprising administering to warm-blooded animals anantioxidatingly effective amount of a composition comprising the formulaof claim
 1. 3. A method of treating free radical-mediated cellulardamage in warm-blooded animals, comprising administering to warm-bloodedanimals an antioxidatively effective amount of a composition comprisingthe formula of claim
 1. 4. A method of inducing antioxidant activity inwarm-blooded animals comprising administering to warm-blooded animals anantioxidatingly effective amount of a biologically active composition,the biologically active composition comprising a compound of thefollowing formula, or an acid or base addition salt thereof:

wherein, X is N—R₅ or O; R₁ is selected from the group consisting ofhydrogen, and, alkyl; R₂ is selected from the group consisting ofhydrogen, alkyl; R₃ is selected from the group consisting of hydrogen,alkyl; R₄ is selected from the group consisting of hydrogen, alkyl; R₅is selected from the group consisting of hydrogen, alkyl; and n is 1 or2.
 5. The method of claim 4, wherein the compound is selected from thefollowing formula:

wherein: R₁ is selected from the group consisting of hydrogen andmethyl; R₂ is selected from the group consisting of hydrogen, methyl,ethyl, t-butyl, pentyl, octyl, phytyl; R₃ is selected from the groupconsisting of hydrogen, methyl and t-butyl; and R₄ is selected from thegroup consisting of hydrogen, methyl, ethyl, t-butyl, pentyl, octyl,phytyl.
 6. The method of claim 4, wherein the compound is of thefollowing formula or an acid or base addition salt thereof:
 7. A methodof treating free radical-mediated cellular damage in warm-bloodedanimals, comprising administering to warm-blooded animals anantioxidatively effective amount of a compound of the following formula,or an acid or base addition salt thereof:

wherein, X is N—R₅ or O; R₁ is selected from the group consisting ofhydrogen, and, alkyl; R₂ is selected from the group consisting ofhydrogen, alkyl; R₃ is selected from the group consisting of hydrogen,alkyl; R₄ is selected from the group consisting of hydrogen, alkyl; R₅is selected from the group consisting of hydrogen, alkyl; and n is 1 or2.
 8. The method of claim 7, wherein the compound is selected from thefollowing formula:

wherein: R₁ is selected from the group consisting of hydrogen andmethyl; R₂ is selected from the group consisting of hydrogen, methyl,ethyl, t-butyl, pentyl, octyl, phytyl; R₃ is selected from the groupconsisting of hydrogen, methyl and t-butyl; and R₄ is selected from thegroup consisting of hydrogen, methyl, ethyl, t-butyl, pentyl, octyl,phytyl.
 9. The method of claim 7, wherein the compound is of thefollowing formula or an acid or base addition salt thereof:

wherein: R₁ is selected from the group consisting of hydrogen andmethyl; R₂ is selected from the group consisting of hydrogen, methyl,ethyl, t-butyl, pentyl, octyl, phytyl; R₃ is selected from the groupconsisting of hydrogen, methyl and t-butyl; and R₄ is selected from thegroup consisting of hydrogen, methyl, ethyl, t-butyl, pentyl, octyl,phytyl.
 10. A compound of the following formula, and acid or baseaddition salts thereof:

wherein, X is N—R₅ or O (when N is 1); or X is O (when N is 2) R₁ isselected from the group consisting of hydrogen, and, alkyl; R₂ isselected from the group consisting of hydrogen, alkyl; R₃ is selectedfrom the group consisting of hydrogen, alkyl; R₄ is selected from thegroup consisting of hydrogen, alkyl; R₅ is selected from the groupconsisting of hydrogen, alkyl.
 11. A compound of claim 10, of followingformula:

wherein: R₁ is selected from the group consisting of hydrogen andmethyl; R₂ is selected from the group consisting of hydrogen, methyl,ethyl, t-butyl, pentyl, octyl, phytyl; R₃ is selected from the groupconsisting of hydrogen, methyl and t-butyl; and R₄ is selected from thegroup consisting of hydrogen, methyl, ethyl, t-butyl, pentyl, octyl,phytyl.
 12. A method of inhibiting the oxidation of compounds ormixtures comprising the addition of an effective amount of a compound ofclaim 10 to said compound or mixture.
 13. The method of claim 12,wherein the compound or mixture may be any base oil or mixture thereofsuitable for the intended use of a lubricant.
 14. The method of claim13, wherein the base oil is selected from the group consisting of aconventionally refined mineral oil, an oil derived from coal tar orshale, a vegetable oil, an animal oil, a hydrocracked oil, or asynthetic oil, or any mixture thereof.
 15. A method of reducing theoxidative environment in a petroleum composition selected from the groupconsisting of lubricating compositions and liquid organic fuels, saidmethod comprising adding to said petroleum composition an effectiveamount of an antioxidant composition, said antioxidant compositioncomprising a compound of claim
 10. 16. A method of inhibiting theoxidation of compounds or mixtures comprising the addition of aneffective amount of a compound of the following formula or an acid orbase addition salt thereof to said compound or mixture:

wherein: R₁ is selected from the group consisting of hydrogen, and,alkyl; R₂ is selected from the group consisting of hydrogen, and alkyl;R₃ is selected from the group consisting of hydrogen, and alkyl; and R₄is an electron-donating substituent.
 17. The method of claim 16, whereinthe compound or mixture may be any base oil or mixture thereof suitablefor the intended use of a lubricant.
 18. The method of claim 17, whereinthe base oil is selected from the group consisting of a conventionallyrefined mineral oil, an oil derived from coal tar or shale, a vegetableoil, an animal oil, a hydrocracked oil, or a synthetic oil, or anymixture thereof.
 19. A method of claim 10, wherein the mixture is apetroleum composition selected from the group consisting of lubricatingcompositions and liquid organic fuels, said method comprising adding tosaid petroleum composition an effective amount of the compound or acomposition comprising the compound.
 20. A method of inducingantioxidant activity in warm-blooded animals comprising administering towarm-blooded animals an antioxidatingly effective amount of abiologically active composition, the biologically active compositioncomprising a compound of the following formula:

wherein: R₁ is selected from the group consisting of hydrogen, and,alkyl; R₂ is selected from the group consisting of hydrogen, and alkyl;R₃ is selected from the group consisting of hydrogen, and alkyl; and R₄is an electron-donating substituent.